You can only install Nero 9 if you purchased a Nero 9 version. You cannot update from Nero 8 to Nero 9. "Updates" are within a same version, so if you want to use a newer version, you need to "upgrade" to Nero 9.

As you reported, you already purchased Nero 9.

When you download the latest Nero 9 update from our web page, it will be a trial version. You will not receive an e-mail when downloading the Nero 9 update or trial version. You will have to launch the trial installation, and use your Nero 9 serial number, the one that you purchased to install Nero 9.